<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>key的作用</title>
</head>
<body>
    <p>
        vue和react都是采用diff算法来对比新旧虚拟结点的，从而更新结点
        Promise构造函数是同步执行还是异步执行,那么then方法呢？
        如何实现一个new?
    </p>
    <script>
        var b = 10;
        (function b(){
            b = 20
            console.log(b)
        })()
    </script>
</body>
</html>